Concrete Posts.

[Egon]

Looking at the pictures makes my back hurt!:thumbsup:

 

[Lloyd_E]

Beppinton... no I don't but I was thinking of running an old very course file across the edge... my good neighbour that showed up after suggested a grinder...

The next pour I will get fancy with some curved(gothic) tops and chamfered edges... will use wood pieces to add to the mould.

egon - that's what the tractor is for. But yes... shovelling and lifting cement bags and all that stuff is laborious but good for the heart too!

We estimated the costs to be just over $6 per post.

2.5 bags of cements at $12 per bag = $30
Stone/sand mix about $6
Pex Pipe: $2.00
Metal Reinforcement: $9

Total: $47 / 8 posts(6 - 4"x4" + 2 - 4"x5") = $5.87 + tax!!!!!!

I've seen them on line for $97.44 per post and up.
PC4600 for 4" x 6" Post

Hopefully this will work.

 

[beppington]

We estimated the costs to be just over $6 per post.

2.5 bags of cements at $12 per bag = $30
Stone/sand mix about $6
Pex Pipe: $2.00
Metal Reinforcement: $9

Total: $47 / 8 posts(6 - 4"x4" + 2 - 4"x5") = $5.87 + tax!!!!!!

That's great! I'm spending $5.97 + 6.25% tax = $6.34 for every 4"x4"x8' PT wood post, & we all know these aren't gonna last forever. And some of them curve after installation, too - You won't have that problem, either.

 

[heehaw]

the 2x6 that will be fastened to the post, is it going to be bolted thru the pvc pipe?? if not how will it be fastened to the post??
heehaw

 

[Whitnel]

One suggestion on the steel you are putting in. For it not to rust it needs to be inside of the concrete at least 1", 2" is usually the min on rebar in slabs. If it is close to the surface it will eventually be exposed and then rust out inside the concrete.

May not be an issues down the road if you are just concerned about breakage during the molding process.

 

[TRR]

You may want to consider a hole thru the post near the top (3 or 4" down) to use for setting the post. Run a cable thru the hole and have your FEL lift the post to set it in the post hole.

 

[Lloyd_E]

heehaw,
Yes the pvc goes through the post. 2x6 will get bolt to post.

Whitnel,
Thanks. Will file away for future reference and use.

TRR,
Good point. I was hoping, naively, that we would just tip the post into the hole from the loader forks. The top hole for the 2x6 is 12' from the top. I could make a sling to go through hole and hook to forks or put a bar through and connect a sling to the bar ends.

We took the ends off the form yesterday... just to see. We are going to leave them a little while more to cook before removing. I also think more release liquid is needed. Also, we may have to look at the sand/aggregate mix. Could be a little more "finer" - I am using left over mix from a project last year. Recent observations, from friends who have seen posts in Europe and England, think a mixture of sand and river pebbles or pea gravel may be better.

 

[Whitnel]

One other thing I though of. Are you vibrating the form at all when pouring. You might experience some honeycombing from trapped air if not. It could be as simple as hitting the form with a hammer during the pouring process.

 

[bcp]

My thought was to build the form on a plywood sheet, but the plywood would not have a frame fastened underneath, just resting on one. When ready to remove the posts, the plywood could be lifted a bit in the center, forming a very mild arch and spreading the form boards away from the posts.

Bruce

 

[sunshine coaster]

I helped make concrete posts about 20 years ago at a community centre, ours were 4x4" posts and if I remember they were about 10 feet tall.
we used to make 2 a day just before leaving, I think we had 6 moulds in total. we made them on a big flat table and were able to strip the mould without moving the post so they dried for at least a few days before moving them.

We put two runs of 1/2 inch rebar in each one and holes for the wire too but i dont remember how we did that now.
Next time I am home (likely next year now) I will have a look and see how they are doing, oh and they are on the beach or almost so pretty harsh conditions for the rebar..

If I were making posts again I would be using the single post per mould method as I remember very little trouble with it...

Oh and we used sand/gravel from the pit and just added our own cement, way cheaper than bags and make it as strong as you like...
Keep up the good work though

oh and edit, we just tapped the forms with a hammer for vibration, not the best method but it seemed to make good posts for us.

 

[forgeblast]

I really like the jig you made. Its a good design that lets you reload it quickly. Very nice job.

 

[RobertBrown]

How did the posts come out Loyd?

 

[RDrancher]

I use a Corner Cat vibrating sander for a cheap concrete vibrator when pouring counter tops in place or casting into forms. Just hold the sander by the end and let the plastic housing that you normally hold onto vibrate against the form.

 

[Lloyd_E]

Robert,

Will be removing from forms tomorrow...


lloyd

 

[Lloyd_E]

Well... this is on going. Some of the posts worked... broke a few trying to get out of form.

1/ redesign form
2/ use more oil
3/ look at mix

The mix I used was a combo of sand/aggregate from concrete plant. Just add portland and water. The ratio was 3:1. I know I added a bit more concrete. The water and final mix gave me a very thick mud - less water makes a stronger mix. Once in the mould a little bit of water pooled on the surface.

I think the aggregate was too large for what I am trying to do - roughly up to 3/4" stone.

On another note: I have a small concrete garden table (18"x24"x2.5" top) which sits on cast concrete legs - think saw horse. It has small (pea gravel or less in size) gravel in it. So, looking at that I think I will rework things and try again...

I did find a site
selling wood posts mounted to a 60" concrete post via a galvanized u-bracket for just under a $100 bucks... this makes it worth trying!!!

 

[MikeD74T]

Lloyd, Use less water in your mix. Stone is where the strength is, most stone is stronger than cement. Remove forms from posts, not posts from forms. Did you wet cure?? Steam cure is even better. Do a search for ferro-cement, wealth of info there, especially on concrete/reinforcement ratios. MikeD74T

 

[Egon]

Consider using 2 mill plastic to line the form with. Cheap and it should separate. Also cosider using slotted end boards to hold the post side pieces in place. Have the slots just a little oversized so the form pieces can come out easily.

Check with a local concrete plant for some proper sizes and graded aggregate as well as a proper cement /water mix.

In industry many items like you are doing are almost a dry mix, formed under pressure and cured in a humidity/ temperature controled environment.

Note: 40 year old data may not be correct any more.

 

[MikeD74T]

Egon, Which "40 year old data" are you refering to? MikeD74T

 

[Egon]

Re: Concrete Posts.
Egon, Which "40 year old data" are you refering to? MikeD74T


I have not kept up to date and as such may be well out of date.

 

[bearhawk]

I would have thought that the form would have to be removed from the post, not remove the post from the form. But I wasn't sure enough to comment.

If you built the form so it could be taken apart, say remove the ends, and then the first part of the side form. Remove the first post. Then remove the next form separator, and continue till the base was empty.